Here are some causes.
It could be the following causes:
- Insufficient motor RPM
- Air leak on suction plumbing
- Blocked/Restricted intake hose
- Filter cap disengaged
- Filter gasket damaged/missing
Here are some solutions:
- Increase motor RPM until pump primes
- Tighten/replace fittings & hose clamps. Verify suction hoses are in good condition.
- Remove blockage from suction line, ensure line is not kinked.
- Lock filter cap into position.
- Replace filter gasket